38 PKOCEEDINGS OF THE ACADEMY OF [1894. 



The view of the morphology and terminology of the periotic cap- 

 sule and adjacent bones as sustained by Prof. Huxley and most other 

 anatomists of the present day is based upon two assumptions : 



1st. That the petro- mastoid portion ot the temporal bone in Man 

 develops from three distinct centers of ossification named respectively 

 prootic, opisthotic and epiotic and represented in the skull of the 

 the lower vertebrata by three bones bearing respectively the same 

 three names and more or less coalesced with each other or adjacent 

 bones. 



2d. That the bone lying in front of the exit of the inferior max- 

 illiary division of the fifth nerve should be regarded in the lower 

 vertebrata as the homologue of the great wing of the sphenoid in Man 

 and named the alisi)henoid, and the bone lying behind such exit as 

 homologous with the upper part of the pars petrosa of Man and 

 named the prootic. 



The conclusion that follows if these two assumptions be admitted, 

 will be that the alisphenoid or homologue of the great wing of the 

 sphenoid is often but little developed or may be even absent in the 

 skull of the lower vertebrata, its place being supplied by the prootic 

 bone or the homologue of the upper part of the pars petrosa of man. 

 Notwithstanding the high authority of Meckel, Kolliker, Huxley 

 and others, among whom may be mentioned the late W. Kitchen 

 Parker, universally conceded while living to be the highest auth()rity 

 on all (luestions pertaining to the develoiMuent and morphology of 

 the skull, the three-fold development of the petro-mastoid portion of 

 the temporal bone has been denied by anatomists and notably by the 

 late Dr. Joseph Leidy. '" 



The author having had occasion recently to study the development 

 of the temporal bone in Man has satisfied himself, at least, that the 

 mastoid portion of the petrosal is not developed from a special centre 

 of ossification but from the petrosal and s(iuaiiiosal portions of the 

 temporal as described by Leidy,'"* and that there is no homologue, 

 therefore, in the skull of Man, of the bone described as the ef)iotic 

 in that of the lower vertebrata. J'urther, while there is no doubt 

 that the petrosal part of the temporal in INlan is developed, as we shall 



"Science, Vol. 1. No. 18. June 8, 1883, p. 507. 

 18 Op. cit. p. 507, Human Anatomy, 1889, p. 116. 



